Mechanical-Hydraulic Pumping System

ABSTRACT

Devices and methods for recovering production fluid from a subterranean formation using a mechanical-hydraulic production system. A mechanical-hydraulic production system is described that includes a power fluid pump, a production fluid pump and a hydraulically-actuated motor that is associated with the production fluid pump to actuate the production fluid pump. The power fluid pump is mechanically driven from the surface to fluid hydraulic power fluid to the motor, thereby driving the production fluid pump to pump production fluid.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to systems and methods for operatingfluid pumps for subterranean production fluid recovery.

2. Description of the Related Art

Enhanced oil recovery techniques often utilize downhole pumps, such aselectrical submersible pumps (ESPs) or progressive cavity pumps (PCPs),to increase the flow rate of hydrocarbons from a well. However, it isdifficult to use these devices in many lateral or deviated wellboreshaving tight radius lateral bends. These bends can damage electricalcables and preclude the use of rigid drive rods for operation of thepumps.

SUMMARY OF THE INVENTION

The invention provides devices and methods for the operation of fluidpumps used for recovery of fluids from subterranean formations. Thesystems and methods of the present invention are particularly suited tooperation of fluid pumps in lateral or deviated wellbores.

An exemplary mechanical-hydraulic pumping system is described thatincludes a mechanically-actuated power fluid pump that is preferablylocated within a proximal area of the wellbore and amechanically-actuated production fluid pump that is preferably locatedin a distal portion of the wellbore. Mechanical operation of the powerfluid pump produces a hydraulic output that is used to power a downholemotor that mechanically drives the production fluid pump. In a describedembodiment, flexible power fluid transmission conduits extend betweenthe power fluid pump and the downhole motor and serve to transmit powerfluid between the power fluid pump and the downhole motor. In adescribed embodiment, the power fluid transmission conduits are coaxial.The described transmission conduits also transmit power fluid that hasbeen exhausted by the downhole motor back to the power fluid pump fromthe motor. Also in a described embodiment, a shroud defines a furtherfluid transmission conduit that extends between the power fluid pump andthe downhole motor to transmit hydrocarbon production fluid from aformation to be produced into production tubing. The production fluidmay be transmitted toward the surface via the production tubing.

In exemplary operation, mechanical power is transmitted from asurface-based mechanical driver, such as a rod drive unit, to the powerfluid pump which is preferably located in a proximal portion of awellbore or other subterranean region. The power fluid pump generates anoutput of power fluid which drives the downhole motor. The downholemotor mechanically drives the production fluid pump which is preferablylocated in a distal portion of the wellbore or other subterraneanregion. In particular embodiments, the proximal portion is asubstantially vertical portion of a wellbore while the distal portion isa deviated or lateral portion of the wellbore.

According to some embodiments of the invention, the exemplarymechanical-hydraulic pumping system includes a fluid accumulator toaccommodate thermal expansion/contraction of the power fluid. Alsoaccording to some embodiments of the invention, the motor includes aspeed increaser which increases the rate of rotation provided by themotor to the production fluid pump.

BRIEF DESCRIPTION OF THE DRAWINGS

For a thorough understanding of the present invention, reference is madeto the following detailed description of the preferred embodiments,taken in conjunction with the accompanying drawings, wherein likereference numerals designate like or similar elements throughout theseveral figures of the drawings and wherein:

FIG. 1 is a side, cross-sectional view of a wellbore containing anexemplary mechanical-hydraulic pumping system constructed in accordancewith the present invention.

FIG. 2 is a cross-sectional view taken along lines 2-2 in FIG. 1.

FIG. 3 is a cross-sectional view of an exemplary accumulator bellowsthat could be used within the pumping system shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts an exemplary wellbore 10 that has been drilled from thesurface 12 down through the earth 14 to a hydrocarbon-bearing formation16. The wellbore 10 has a substantially vertical portion 18 and alateral, deviated portion 20 which are interconnected by angular bend22. The substantially vertical portion 18 is proximate the opening 17 atthe surface 12 (i.e., a proximal portion of the wellbore 10), while thelateral portion 20 is in a distal portion of the wellbore 10.Perforations 24 extend outward from the lateral portion 20 into theformation 16. Although perforations 24 are shown in the describedembodiment, it will be understood that these are depicted as an exampleof a wellbore and are not necessary to the invention. The systems andmethods of the present invention may be used in open hole wellbores orother wells which do not have perforations. In particular embodiments,at least the substantially vertical portion 18 of the wellbore 10 islined with casing 19, of a type well known in the art. Also inparticular embodiments, the casing 19 is provided with a gas removalport 21 which permits gas within the casing 19 to escape the casing 19.

An exemplary mechanical-hydraulic pumping system, generally indicated at26, is disposed within the wellbore 10. The system 26 includes amechanically-driven power fluid pump 28 which is disposed within thesubstantially vertical portion 18 of the wellbore 10. The power fluidpump 28 includes a lower pump section 30 and an upper seal section 32,as is known in the art. In one embodiment, the exemplary power fluidpump 28 is actuated by rotation of drive rod 34. Drive rod 34 extendsfrom the seal section 32 to the surface 12 within production tubing 35and is rotated at the surface 12 by a mechanical driver in the form of arod drive unit 36. In an alternative embodiment, the power fluid pump 28is actuated by axial reciprocation of rod 34 by the rod drive unit 36.Suitable pumps for use as the power fluid pump 28 include any of anumber of electrical submersible pumps or progressive cavity pumps whichare available commercially from Baker Hughes Incorporated of Houston,Tex. In particular embodiments, the rod drive unit 36 is operable torotate (or axially reciprocate) the rod 34 at variable speeds.

A production fluid pump, mechanically-actuated fluid pump 38, isdisposed within the lateral portion 20 of the wellbore 10. Theproduction fluid pump 38 includes fluid intake openings 40 and fluiddischarge openings 42. The production fluid pump 38 may be an ESP or aPCP style pump. Suitable fluid pumps for use as the production fluidpump 38 include a number of ESP or PCP pumps which are availablecommercially from Baker Hughes Incorporated. A downhole hydraulic motor44 is affixed to the production fluid pump 38. The motor 44 uses thepower fluid supplied by the power fluid pump 28 to cause rotationalenergy. In particular embodiments, the motor 44 includes a speedincreaser which will increase the rate of rotation that is transmittedfrom the motor 44 to the second fluid pump 38. In particularembodiments, the speed increaser of the motor 44 is a gearingarrangement that converts rotation at a lower speed to rotation at ahigher speed. A suitable component for use as the speed increaser is adevice known in the industry as a gear box. For example, if the powerfluid provided by the motor 44 generated a rotational speed of about 500RPM, the speed increaser might use gears having a ratio of 7:1 toincrease the rate of rotation applied to the production fluid pump 38 to3500 RPM. Suitable motors for use as the hydraulic motor 44 any of anumber of motors for driving downhole pumps which are availablecommercially from Baker Hughes Incorporated. In operation, the hydraulicmotor 44 uses hydraulic power fluid as a power input to drive theproduction fluid pump 38 mechanically. The production fluid pump 38draws hydrocarbon production fluid into the intake openings 40 andexpels the production fluid through the discharge openings 42. Gas thatis within the casing 19 is removed from the casing annulus by gasremoval port 21. Some gas, or substantially all gas, may also beproduced through the production fluid pump 38 and through the productiontubing 35, depending upon the application and the selection of pump 38.

Flexible hydraulic power fluid conduits 46, 48 extend between the powerfluid pump 28 and the hydraulic motor 44 that is associated with theproduction fluid pump 38. In the embodiment depicted in FIGS. 1 and 2,these conduits 46, 48 are coaxial. However, in an alternate embodiment,the conduits 46, 48 are not coaxial but are, instead, separate, parallelconduits. In the exemplary embodiment, the coaxially inner conduit 46 isa power fluid supply conduit that transmits hydraulic power fluidexiting the first fluid pump 28 to the motor 44. Also in the exemplaryembodiment, the outer coaxial conduit 48 is a power fluid return conduitthat returns hydraulic power fluid from the motor 44 to the first fluidpump 28.

A flexible shroud 50 radially surrounds the power fluid pump 28, thehydraulic power fluid conduits 46, 48, the hydraulic motor and speedincreaser 44, and the discharge openings 42 of the production fluid pump38. At its proximal end, the shroud 50 is interconnected with theproduction tubing 35. At its distal end, the shroud 50 is affixed to theproduction fluid pump 38. In particular embodiments, the shroud 50 isformed of resilient steel, polymer or composite material and hassufficient pressure capability and integrity to handle the fulldischarge pressure of the production fluid pump 38.

In operation, the rod drive unit 36 rotates the drive rod 34 tomechanically operate the power fluid pump 28. In an alternativeembodiment, the drive rod 34 is axially reciprocated to operate thepower fluid pump 28. The power fluid pump 28 flows hydraulic power fluidas an output through the power fluid supply conduit 46 to the hydraulicmotor and speed increaser 44. Power fluid that is exhausted by thehydraulic motor and speed increaser 44 is returned to the power fluidpump 28 through the power fluid return conduit 48. The hydraulic powerfluid causes the production fluid pump 38 to draw hydrocarbon productionfluid in through the intake openings 40 and expel it through thedischarge openings 42. Expelled hydrocarbon production fluid is flowedthrough the shroud 50 to production tubing 35. The production fluid willthen flow through the production tubing 35 upwardly toward the surface12 wherein it will exit the production tubing 35 into production line52.

In particular embodiments, a fluid accumulator 54, of a type known inthe art, is associated with the power fluid conduits 46, 48 toaccommodate increases and decreases in fluid volume due to thermalexpansion and contraction. FIG. 3 depicts an exemplary fluid accumulator54 that is incorporated into the production fluid pump 28 below the pumpsection 30. The exemplary fluid accumulator 54 includes an outer housing55 which houses an expandable elastomeric bladder 56 that interconnectswith the lower pressure power fluid return conduit 48. It is noted thatthe passage of production fluid past the power fluid pump 28 will helpto cool the power fluid pump 28 and associated gear box speed increaser.

The systems and methods of the present invention permit a mechanicaldrive means at surface 12, such as rod drive unit 36 to mechanicallyoperate a power fluid pump 28 which, in turn, operates a productionfluid pump 38 that is driven by hydraulic power fluid. Thus, theinvention provides a power transmission system that can operateefficiently and reliably in deviated wells. Systems constructed inaccordance with the present invention are capable of producinghydrocarbon fluid through any reasonable radius lateral bend 22 withoutconventional concerns relating to side loading of sucker rods or ESPcables being damaged. In addition, the systems and methods of thepresent invention allow for the intake openings 40 of the second pump 38to be placed anywhere within the lateral section 20 of the wellbore 10.

According to exemplary methods of the present invention, amechanical-hydraulic pumping system 26 constructed in accordance withthe present invention is disposed within the wellbore 10 such that thepower fluid pump 28 is located within a proximal portion of the wellbore10, and, in particular, the substantially vertical portion 18. Theproduction fluid pump 38 is disposed within a distal portion of thewellbore 10, and in particular, the lateral deviated portion 20.Thereafter, the rod drive unit 36 mechanically drives the power fluidpump 28 via rotation or axial reciprocation of the drive rod 34.Actuation of the power fluid pump 28 in this manner will flow hydraulicpower fluid along the power fluid supply conduit 46 to operate thedownhole motor 44. The motor 44, in turn, drives the production fluidpump 38 to draw production fluid into the shroud 50.

Those of skill in the art will recognize that numerous modifications andchanges may be made to the exemplary designs and embodiments describedherein and that the invention is limited only by the claims that followand any equivalents thereof.

1. A mechanical-hydraulic pumping system for use in flowing fluid from asubterranean formation, the system comprising: a power fluid pump to beplaced in a proximal portion of a wellbore; a production fluid pump tobe placed in a distal portion of a wellbore; a hydraulically-actuatedmotor associated with the production fluid pump to actuate theproduction fluid pump; and the power fluid pump flowing hydraulic powerfluid to the motor to drive the motor and production fluid pump.
 2. Thepumping system of claim 1 further comprising a fluid transmissionconduit for flowing production fluid pumped by the production fluid pumpfrom the formation.
 3. The pumping system of claim 1 wherein the powerfluid pump is associated with the motor by: a power fluid supply conduitto transmit hydraulic power fluid from the power fluid pump to themotor; and a power fluid return conduit to transmit power fluid from themotor to the power fluid pump.
 4. The pumping system of claim 3 whereinthe power fluid supply conduit and the power fluid return conduit arecoaxial.
 5. The pumping system of claim 1 further comprising a fluidaccumulator to accommodate thermal expansion and contraction of thehydraulic power fluid.
 6. The pumping system of claim 3 furthercomprising a fluid reservoir associated with the power supply and returnconduits to permit cooling of power fluid.
 7. The pumping system ofclaim 1 further comprising a mechanical driver for operation of thepower fluid pump.
 8. The pumping system of claim 7 wherein themechanical driver comprises a rod drive unit to rotate a drive rod thatactuates the power fluid pump.
 9. The pumping system of claim 7 whereinthe mechanical driver comprises a rod drive unit to axially reciprocatea drive rod that actuates the power fluid pump.
 10. The pumping systemof claim 1 wherein the power fluid pump comprises an electricalsubmersible pump.
 11. The pumping system of claim 1 wherein the powerfluid pump comprises a progressive cavity pump.
 12. The pumping systemof claim 4 further comprising a transmission conduit for flowingproduction fluid pumped by the production fluid pump from the formation,the transmission conduit being defined within a shroud that radiallysurrounds the power fluid supply conduit and power fluid return conduit.13. A mechanical-hydraulic pumping system for use in flowing fluid froma subterranean formation, the system comprising: a power fluid pump tobe placed in a proximal portion of a wellbore; a production fluid pumpto be placed in a distal portion of a wellbore; a hydraulically-actuatedmotor associated with the production fluid pump to actuate theproduction fluid pump; the power fluid pump flowing hydraulic powerfluid to the motor to drive the motor and production fluid pump; and afluid transmission conduit for flowing production fluid pumped by theproduction fluid pump from the formation.
 14. The pumping system ofclaim 13 wherein the power fluid pump is associated with the motor by: apower fluid supply conduit to transmit hydraulic power fluid from thepower fluid pump to the motor; and a power fluid return conduit totransmit power fluid from the motor to the power fluid pump.
 15. Thepumping system of claim 14 wherein the fluid transmission conduit isdefined within a shroud that radially surrounds the power fluid supplyconduit and power fluid return conduit.
 16. A method of recoveringproduction fluid from a subterranean formation comprising the steps of:a) disposing a mechanical-hydraulic pumping system within a wellboreformed down to the formation, the pumping system having a power fluidpump, a production fluid pump, a hydraulically-actuated motor associatedwith the production fluid pump to actuate the production fluid pump; b)mechanically driving the power fluid pump with a mechanical driver tooutput hydraulic power fluid; c) flowing the hydraulic power fluid fromthe power fluid pump to the motor to drive the motor and productionfluid pump, the production fluid pump drawing production fluid from thesubterranean formation.
 17. The method of claim 16 wherein the step ofmechanically driving the power fluid pump further comprises rotating adrive rod by a rod drive unit to actuate the power fluid pump.
 18. Themethod of claim 16 wherein the step of mechanically driving the powerfluid pump further comprises axially reciprocating a drive rod by a roddrive unit to actuate the power fluid pump.
 19. The method of claim 16further comprising the step of transmitting production fluid from theproduction fluid pump to a surface location.
 20. The method of claim 16wherein the step of disposing a mechanical-hydraulic pumping systemwithin a wellbore further comprises: disposing the power fluid pump in aproximal portion of the wellbore, and disposing the production fluidpump in a distal, deviated portion of the wellbore.